Field of the Disclosure
The present disclosure relates in general to integrated circuit devices, and more specifically to DC offset calibration of wireless receivers.
Description of the Related Art
Direct conversion receivers convert an RF carrier waveform directly to a baseband frequency. Receiver impairments such as inadequate carrier suppression, 2nd order inter-modulation, mismatches and inherent offsets in the active circuits of the receiver front end all contribute to a DC offset in the down-converted baseband signal. This DC offset can seriously impede normal operation of a receiver by causing saturation, automatic gain control failure, analog-to-digital converter (ADC) dynamic range waste and/or incorrect demodulation by a modem.
DC offset compensation is often used in direct conversion receivers. Factory calibration of DC offsets increases production cost and mechanisms are required to store and manage the data on the device, however. Additionally, DC offsets vary with gain and frequency, so calibration over-all operating conditions can take a lot of time and generate a large amount of data that can consume an impractical amount of space on an integrated circuit die. Alternatively, DC offset calibrations done over only a small subset of radio conditions will be suboptimal for a set of radio operational conditions leading to poor performance. Moreover, any DC offset factory calibration done on an RF part does not capture any DC impairments that might be specific to the final build configuration of a radio.